A program of exploratory research is proposed on the structure of family interaction and on the strategies that family members take within that organization. The research would begin with intensive study of normal family interaction and proceed to more problematic family interaction, once sufficient initial results have been produced to permit meaningful contrasts. The approach to studying interaction structure includes a carefully developed set of procedures for transcribing speech (both language and paralanguage) and body motion, for detecting and analyzing patterns of interaction sequences, and for describing results. Interaction structure is described in terms of rules applying to action sequences involving two or more participants. In this manner, the structure of family interaction is both holistic (involving all participants, as opposed to focussing on the messages of an individual) and bahaviorally inclusive. Once hypotheses are developed concerning family interaction structure, it is possible to study in a systematic way interaction strategy; the manner in which each participant operates within the structure. To facilitate a rapid start on actual data analysis, the research would begin with a large pool of videotapes already made. These tapes were made of everyday interaction in the homes of two families with a normal, first-born child, extending in one case from 9 to 18 months, and in the other, from 9 to 22 months. For two consecutive days each month taping began before breakfast and continued through bedtime, including about two hours of actual interaction each day. Careful transcription of speech and body motion would be carried out on these tapes, and the resulting data searched for structural pattens. The purpose of the research is to achieve detailed, specific descriptions of the structures and strategies of family interaction that permit higher level statements concerning the nature and complexity of the family interactive system and of the child's communicative competence. The descriptions would permit effective contrasts of interaction processes both developmentally within a family and with respect to mental health between different families.